Categories
Internal Medicine

Portal hypertension

Introduction

↑ Pressure in portal venous system. (> 12 mmHg)

  • Normal portal pressure: 5-10 mmHg
  • Liver receives 25% cardiac output through dual vascular supply:
    • Portal venous circulation: 75–80% blood supply (low-pressure system)
    • Hepatic artery: 20-25% (high-pressure system)

Aetiology

Prehepatic (portal vein):

  • Portal venous thrombosis
  • Extrahepatic portal venous obstruction (EHPVO) (M/C cause, 50-75%)
    • Cavernous transformation of portal vein
  • Isolated splenic vein thrombosis

Intrahepatic (liver):

  • Liver cirrhosis (2nd M/C, 25-35%)
  • Non-cirrhotic portal fibrosis (NCPF) (10-15%)
  • Congenital hepatic fibrosis
  • Veno-occlusive disease
  • Noncirrhotic portal fibrosis
  • Schistosomiasis
  • Sarcoidosis
  • Nodular regenerative hyperplasia

Posthepatic (heart, CVC, hepatic Veins):

  • Budd-Chiari syndrome (hepatic vein or inferior vena cava obstruction) (8–26%)
  • Constrictive pericarditis
  • Right-sided heart failure

Pathophysiology

jvim_691_f2
Pathophysiology of intrahepatic sinusoidal portal hypertension and ascites formation in cirrhosis. Increases in the intrahepatic vascular resistance (IHVR) occur because of mechanical (fibrosis in the sinusoids, microthrombi in hepatic veins, and regenerative nodule formation) and dynamic (failure of sinusoidal relaxation) obstructive processes within the liver. At the same time, the splanchnic circulation undergoes progressive vasodilatation, leading to increases in portal blood flow (PBF) that further increase portal vein pressure. Systemic compensation for the splanchnic arterial vasodilation creates a hyperdynamic circulation marked by increased cardiac output (CO) and decreased peripheral vascular resistance (PVR). Progressive splanchnic vasodilatation, however, leads to eventual failure of this circulatory response and development of systemic vasodilatation and hypotension. This decrease in effective circulatory blood volume leads to activation of the renin‐angiotensin‐aldosterone‐sympathetic system (RAAS) and the nonosmotic release of antidiuretic hormone (ADH). This leads to avid renal sodium and water retention creating a volume overload and the development of ascites. | ATII, angiotensin II; CO, carbon monoxide; ET, endothelin; NE, norepinephrine; NO, nitric oxide. | Buob, S., Johnston, A. N., & Webster, C. R. L. (2011). Portal Hypertension: Pathophysiology, Diagnosis, and Treatment. Journal of Veterinary Internal Medicine, 25(2), 169–186. https://doi.org/10.1111/j.1939-1676.2011.00691.x

Clinical features

  • GI bleed (M/C presentation):
    • M/C d/t oesophagal varices
  • Ascites (hepatic decompensation)
  • Caput medusae
  • Diminished liver function
  • Splenomegaly

Complications

Ascites (free fluid in the peritoneal cavity):

PH → Endothelial NO release in blood vessels → Hypotension → Compensatory aldosterone release (kidneys) → Increased water retention → Pooling of blood

Dilutional (hypervolemic) hyponatremia:

PH → Endothelial NO release in blood vessels → Hypotension → Compensatory aldosterone release (kidneys) → Increased water retention → Hyponatremia
  • Marker of late-stage disease and a negative prognostic indicator

Hepatorenal syndrome:

Reversible renal failure as a consequence of profound renal vasoconstriction secondary to the release of angiotensin, norepinephrine, and ADH in response to splanchnic vasodilatation

Pulmonary complications:

Microvascular pulmonary arterial dilatation (most likely because of NO overproduction in the lung) leading to ventilation‐perfusion mismatch.
  • Hepatopulmonary syndrome:
    • Triad:
      1. Chronic liver disease/portal hypertension
      2. Alteration of arterial oxygenation
      3. Intrapulmonary vascular dilatations
  • Portopulmonary syndrome 
    • Pulmonary arterial hypertension (>25 mmHg)
  • Hepatic hydrothorax: Pleural effusion with hepatobiliary disease
    • Because of direct passage of ascites from abdomen to thorax through undetectable diaphragmatic rent

Spontaneous bacterial peritonitis (8–30% in cases with ascites):

  • Mortality: 20–40% if untreated
  • Asymptomatic or abdominal pain, fever, and diarrhea
  • Neutrophil >250 cells/mm3 in ascitic fluid (DIAGNOSTIC, regardless of pathogen detection)

Hypersplenism:

Congestive splenomegaly and ↑ hemolysis by the enlarged spleen.
  • Pancytopenia

Portal hypertensive gastropathy:

Mucosal and submucosal vascular ectasia in the absence of inflammation.
  • Impairment of gastric mucosal defence
  • Thrombosis of mesenteric vessels (d/t circulatory stasis)
  • Alterations in gastrointestinal motility
  • Bacterial overgrowth (lack of intestinal bile acids)
  • Mucosal oedema (↑ gastrointestinal mucosal permeability)

Acquired portosystemic shunts:

  • Anorectal varices: May bleed and cause blood in stool: Hematochezia
  • Oesophageal varices: May bleed and cause vomiting of blood: Haematemesis
  • Caput medusae: Swollen veins on the anterior abdominal wall
  • Haemorrhoids: Swollen or dilated hemorrhoidal veins

Hepatic encephalopathy (neurocognitive impairment):

↓ Liver function & ↓ blood detoxification → Toxic metabolites cross BBB
  • Clinically manifested as a range of signs from subtle behavioural deficits to stupor and coma.

Liver failure:

  • Palmar erythema
  • Gynecomastia
  • Spider naevi
  • Loss of axillary and pubic hair

Diagnosis

Hepatic venous pressure gradient (HVPG) (GOLD STANDARD):

Assess severity of portal hypertension. HVPG is calculated as the difference between the wedged hepatic vein pressure (WHVP) and free hepatic vein pressure (FHVP).
  • Portal hypertension is defined as HVPG ≥ 5 mmHg
    • Clinically significant when > 10-12 mmHg
jvim_691_f1
Schematic representation of the anatomic classification of portal hypertension (PH). Portal hypertension can be because of prehepatic, intrahepatic (presinusoidal, sinusoidal or postsinusoidal) and posthepatic causes. Indirect evaluation of portal venous pressure (PVP) can be obtained by catheterization of the caudal vena cava and advancement of the catheter into the hepatic veins. This permits measurement of the free hepatic vein pressure (FHVP), which reflects caudal vena cava pressure. Measurement of the wedged hepatic vein pressure (WHVP) is accomplished by occluding the hepatic vein by inflation of the catheter balloon. WHVP is a measure of sinusoidal pressure which in the normal state is slightly lower (about 1 mmHg) than PVP. The hepatic venous pressure gradient (HVPG) is calculated as the difference between the WHVP and FHVP. This gradient is increased with intrahepatic sinusoidal and postsinusoidal PH, but not with prehepatic and presinusoidal intrahepatic PH (where both WHVP and FHVP are usually normal) or with posthepatic PH (where WHVP, FHVP and central venous pressure, CVP, are elevated). | Buob, S., Johnston, A. N., & Webster, C. R. L. (2011). Portal Hypertension: Pathophysiology, Diagnosis, and Treatment. Journal of Veterinary Internal Medicine, 25(2), 169–186. https://doi.org/10.1111/j.1939-1676.2011.00691.x

Imaging:

  • Ultrasonography (USG)
    • First-line imaging technique for the diagnosis and follow-up
    • Findings:
      • Dilated portal vein (diameter > 13 or 15 mm)
  • Doppler ultrasonography
    • Slow velocity of <16 cm/s + to dilatation in the MPV (DIAGNOSTIC)
513px-portalhypertension28revascuofumbilicalvein29mark
Portal hypertension due to cirrhosis resulting in revascularization of the umbilical vein | James Heilman, MD – CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=49213115

Management

  • Beta-blockers (propranolol):
    • ↓ Portal venous pressure
    • Prevent complications

Ascites:

  • Sodium restriction
  • Diuretics (↓ fluid overload)

Bleeding oesophageal varices (MEDICAL EMERGENCY):

  • Octreotide
  • Balloon tamponade
  • Sclerotherapy
  • Variceal ligation

Transjugular intrahepatic portal systemic shunt (TIPS):

Introduced through the right internal jugular vein, catheterization of a main hepatic vein, transparenchymal catheterization of the portal vein, and serial dilation of the track until large enough to insert a stent. Once placed the stent is dilated sufficiently to reduce the portal-systemic gradient below 12 mmHg.
  • Success rate: 92–99%
  • Absolute contraindications: Right-sided heart failure, severe liver failure and polycystic liver disease
  • Relative contraindications: Hepatic tumours, encephalopathy and hepatic/portal vein thrombosis
  • Complications: Acute stent thrombosis, hemobilia, stent migration and others related to angiography in general
Fluoroscopic_image_of_transjugular_intrahepatic_portosystemic_shunt_(TIPS)_in_progress
TIPS, shown in progress here, has been shown to improve kidney function in individuals with HRS if portal pressures decrease after the procedure. A catheter has been passed into the hepatic vein and after needle puncture, a guidewire was passed into a portal vein branch. The tract was dilated with a balloon, and contrast injected. A self-expandable metallic stent has yet to be placed over the wire. | By Samir at en.wikipedia, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=7389846

Leave a Reply

%d